I think for myself I would go the mixing desk route and use the computer as Forrest does, however it will require a major shuffling of gear. I have worked at bring the audio production quality of my studio components up over the years and have reach its zenith all of which is focused on a 2 channel input daw system. With a mixer Id want multi track recording capabilities which would mean more converters for example, so it will take quite bit of reconfiguring and solution thinking.
An analog mixer is going to add more grunge to your sound then any decent multi-channel converter will at this stage, most of them are pretty good these days I feel.
I just recently acquired a Soundcraft Ghost mixer and am having a go at using a mixer again instead of doing everything in the box. I have to say it's nice to have everything in front of you, but I still feel a bit compromised. I may still go back to running everything direct into the computer and using Logic as my mixer again. The main draw back going that route being you need a large interface, basically inputs for all your synths, as well as for your effects and outputs for those too. Also, you have to turn your computer on and boot up Logic if you want to work on anything.
Ok so here are a few things I would recommend and that you should be aware of if you are going to go the mixer route:
1. Get as many channels as you can afford. I have a 24 channel Ghost and a lot of gear, and I just don't have enough channels. I'm actually thinking about downsizing because of this.
. Steve Roach has a 48 channel board in his studio and I can tell you he uses just about all of the channels. If you have a lot of gear you'll need a lot of channels.
2. Get a board with as many aux sends as you can get. Stereo auxs are even better. My board has 8 auxs which is great but since the Ghost is an inline board and has basically 2 inputs not all the auxs go to the main input, some are dedicated to the secondary input which means they are not useful. I might in the future modify the board so that all the auxs are on the main channel but will have to wait.
3. Be prepared to loose a lot of space in your studio. Boards take up a lot more room.
4. Boards require more cables, getting a board will more that double the amount of cables requiremented.